In the past, there has been known an air pollution control system that treats a flue gas discharged from a boiler installed in a thermal power facility or the like. The air pollution control system includes a denitration apparatus that removes nitrogen oxides from the flue gas discharged from the boiler, an air heater that recovers heat of the flue gas having passed through the denitration device, a precipitator that removes soot and dust contained in the flue gas after heat recovery, and a desulfurization apparatus that removes sulfur oxides contained in the flue gas after dust removal. As the desulfurization apparatus, a wet desulfurization apparatus is generally used, which removes sulfur oxides contained in a flue gas by bringing a limestone absorbent or the like into gas-liquid contact with the flue gas.
Recently, due to enhancement of wastewater regulation, elimination of wastewater in an air pollution control facility has been earnestly desired and an advent of an air pollution control facility for achieving the elimination of wastewater has been earnestly desired in which an operation can be stably performed.
As a facility for performing the elimination of wastewater, the applicant has previously proposed a technique in which a spray drying apparatus is used to dry dehydrated filtrate obtained by separating gypsum from desulfurization wastewater and the desulfurization wastewater is spray-dried using a boiler flue gas (Patent Literature 1).